Big difference, coming from Ultegra 6600. Stopping from 40mph only requires a few feathered pulls from the lever and the bike comes to a rapid halt. With Ultegra, I needed long, hard lever action and the brakes got so hot, I thought the tube was going to pop...not with DA 7800!

Get them if you can still find them. Dura Ace 7900 is way over rated and prohibitively expensive.

I finally upgraded my 20 year-old Dura Ace 7402 calipers to the 7800 model. They are lighter than the old single-pivots, and although they are a little fussy to set up, once dialed in, the performance is astonishing. In, fact, it is quite easy to lock up the rear wheel if you are not careful, due to the awesome stopping power.
Be sure to grease all the bolts upon installation, especially the tiny brake pad retention bolts, and don't overtighten the brake shoe fixing bolts, lest you crack the thin concave toe-in washers, which are essential for mounting the brake shoes.

I can not believe the improvement in stopping since switching to these brakes. I replaced a vintage set of Suntour Superbe Pro's that I had held on to for too long for sentimental reasons. My least favorite 15 percent downhill has now become my favorite, allowing me to confidently spin up to speed and quickly bleed it back off heading into the corners. I replaced the stock pads with Kool Stop Salmon's, and surprisingly I think the stock Shimano pads are actually better. In any case the Kool Stops are at best over-rated.